Tubing.



No. 840,766. PATENTED JAN. a, 1907. E. T. GREENFIELD.

TUBING.

APPLICATION FILED OCT. 30.1905. I

wnwtslsss: INVENTOR I 1 ATTORNEY TIE ern n W EDWIN T. GREENFIELD, OF KIAMESHA, NEW YORK.

TUBING.

Specification of Letters Patent.

Patented an. s, 1907.

To all whom it may concern.-

Be it known that I, EDWIN T. GREENFIELD, of Kiamesha, in the county of Sullivan and State of New York, have invented certain new and useful Improvements in Tubing, of which the following is a specification.

The invention concerns flexible spirallywound interlocking tubing (preferably metallic) of the character employed as conduit containing an electrical conductor or conductors and as armoringfor electric cables, hose, and the like.

' One of the objects of the invention is to provide an improved article of this character having maximum strength without, however, sacrificing the desirable feature of flexibility.

A further object is to provide a structure which may be manufactured with greater ease and at higher speed than is now possible.

The invention may be expressed in tubing formed of one or more strips bent into successive spirals having interlocking edges, tubing so constructed having been disclosed in several patents heretofore granted to me as, for example, No. 630,503, Figures 1 and 3. The material (usually steel) of which such tubing is constructed is required to be of such thickness as to adapt the same for practical use for the purpose desired. Naturally as the thickness is increased greater difliculty is experienced in the forming operation and more power and slower speed are required. Under the present invention these objections are overcome by employing instead of a strip of the full thickness required two strips each of substantially one-half such thickness, these being formed, as the single strip of full thickness is formed, by bending or winding and lying in spiral form arallel with and adj acent to each other.

I ave found that such parallel and adjacent strips can be given the proper-lateral curvature and also spirally formed tocomplete the tube by the use of less power and at greater speed than are required in the production of tubing from a single integral strip of the full thickness necessary.

Within the scope of this invention the tubing may be formed of a single pair of such half-thickness strips or of two pairs of such strips, as will be understoodupon reference to the patent above named. For the purpose of this disclosure 1 have illustrated the former construction in the drawings, in which Fig. 1 is a side elevation, and Fig. 2 a longitudinal section. I

In the production of this tubing, two (preferably metallic) strips a a, each of approximately one-half the thickness required for the walls of the tube, are laid together, one on the other, and passed simultaneously through a suitable die or dies, whereby they are laterally curved, so that the successive spirals shall interlock while remaining movable relatively to each other to assure flexibility.

After being given this lateral curvature the strips are formed into such successive interlocking spirals in any suitable manner-as,

-' overlying the pair first named being ivena laterally-convex sha e, all as will rea 'ly be understood by one s illed in the art.-

What I claim is 1. A tube consisting of a series ofspiral formed of a plurality of thicknesses of mate rial of equal width and one directly overlying another, the adjacent edges of said splrals,

being interlocked, substantially as set forth. 2. A tube consisting of a series of spirals formed of a plurality of thicknesses of material of equal width and one directly overlying another, said thicknesses being similarly curved transversely and said spirals being interlocked at their adjacent edges, substantial] as set forth.

T is specification signed and witnessed I this 26th day of October, 1905. 1

EDWIN T. GREENFIELD; Witnesses:

I. MoINTosH, S. O. EDMONDS. 

